Bug 964196: Give nfcd access to wake locks

This patch changes the group of the nfcd process to 'system', so
that nfcd has access to the wake-lock interface in /sys/power/.

Signed-off-by: Thomas Zimmermann <tdz@users.sourceforge.net>
Merge pull request #144 from tdz/bug-964196

Bug 964196: Give nfcd access to wake locks